To provide a point-to-line light source converting light guide body which can effectively convert a point light source to a line light source having an even brightness while realizing cost reduction and size reduction and which can be preferably used as a line light source for an end face of a light guide plate.

Light from point light sources 5a and 5b are introduced into a transparent rod-like body via both end faces 1c and 1d. A diffraction grating is provided on a side face 1b of a transparent rod-like body. The diffraction grating diffracts incident light I so that the light is emitted from another side face 1b. A grating part 3 and a non-grating part 4 comprise a unit width W and plural diffraction grating parts 3 are provided with certain spacing. The ratio between the width of the grating part and the width of the non-grating part within each unit width W is changed so that the brightness at the other side face 1b is high and uniform.